The present invention relates to improvements in vapor recovery sealing devices employed in discharging liquids into a tank.
The sealing device of the present invention finds particular utility in preventing atmospheric contamination in filling large, bulk transport tanks such as are found on tanker trucks and railway tank cars for the transport of liquids such as fuel, acids, alkalis and other liquid chemical products. The vapors of such products are hazardous in various fashions when they escape into the atmosphere and become airborne.
This problem of atmospheric contamination is similar to the more widely recognized problem of pollution from gasoline vapors generated in filling vehicle fuel tanks. The latter problem has been adequately overcome by vapor recovery fuel nozzles. However, there are significant differences between filling a vehicle fuel tank and filling large, bulk tanks.
In bulk transport tanks, it is a widely accepted practice to discharge liquids through a large opening in the top of the tank. Conventionally the liquid is discharged into the tank by an articulated conduit system known as a loading boom. The conduits are large and of sufficient size to discharge liquids at rates of up to 50 to 100 gallons per minute or more.
There have been previous proposals for vapor recovery sealing devices adapted for use in filling such bulk transport tanks.
In one such device a plate overlays an upstanding flange, which commonly defines the manhole opening. J-hooks are then employed to engage the inner surface of the top of the tank to draw the plate into sealing engagement with the top of the flange. The device is mounted on the discharge end of a loading boom. One passage through the sealing plate permits discharge of liquid there through. Another passage provides for the flow of vapor from the tank to conduit means which extend to a remote location at which the vapors are condensed and/or otherwise safely disposed of.
Another prior proposal is similar in general function, but is provided with a conical member which sealingly engages an inner diameter surface defining the manhole opening.
These prior devices, while capable of fulfilling the basic vapor recovery function, have several shortcomings.
Primarily these shortcomings stem from the fact that there is a wide variation in the configuration of manholes from one bulk transfer tank to another.
The prior devices are limited in the range of variation in manhole configurations with which they can be used.
Another shortcoming of the prior devices is in the difficulties which can be encountered in obtaining an effective seal with the manhole opening.